The present invention relates to a hermetic scroll compressor and, more particularly, to an improvement for preventing an oil rise in which lubricating oil is accompanied by discharged gas and exits the compressor.
A hermetic scroll compressor is often used to compress refrigerant gas for an air conditioning system. Generally, the hermetic scroll compressor comprises a closed housing, a compressor component accommodated in an upper portion of the closed housing, and an electric motor accommodated in a lower portion of the closed housing for driving the compressor component. An oil reservoir for lubricating oil (hereinafter, also referred merely to "oil") is defined below the electric motor. The compressor component comprises fixed and orbiting scrolls each having their respective spiral wraps in the form of an involute or close thereto, which are in mesh with each other. The orbiting scroll is driven by a crankshaft such that the orbiting scroll moves in orbital motion without rotation about its own axis, relative to the fixed scroll. The crankshaft is driven by the above-mentioned electric motor. The fixed scroll, the orbiting scroll and the crankshaft are supported by a frame fixedly arranged within the closed housing. The oil is drawn up from the oil reservoir into an oil passage in the crankshaft to lubricate each bearing and sliding surfaces of the scrolls. Subsequently, the oil is discharged, together with refrigerant gas compressed at the compressor component, into a space within the closed housing above the compressor component. The discharged oil passes through a refrigerant passage defined between the frame and an inner peripheral wall surface of the closed housing, and enters a space below the frame. The oil further passes through refrigerant passages defined between the electric motor and the closed housing, and is returned to the oil reservoir. On the other hand, the refrigerant gas cools the electric motor and, subsequently, is discharged to the outside of the closed housing through a discharge pipe connected to the closed housing.
In the conventional hermetic scroll compressor, disclosed for example, in Japanese Patent Application Laid-Open Nos. 57-198384 and 60-224991, a refrigerant passage is provided which extends from the space within the closed housing above the compressor component, to the neighborhood or an upper coil end of the electric motor through a location between the frame and the inner peripheral wall surface of the closed housing. Separation of the oil contained in the refrigerant depends upon effects due to a change in velocity when the refrigerant impinges against the upper end of the electric motor and due to a reduction in velocity of the refrigerant at the outer periphery and a lower portion of the electric motor.
A disadvantage of the above-described prior art resides in the fact that when large amounts of oil are contained in the refrigerant, the oil is collected or stays on the upper portion of the electric motor, and the refrigerant gas impinges against the collected oil. By this reason, the oil is not sufficiently separated from the refrigerant. Conversely, the oil on the upper portion of the electric motor is blown up by the refrigerant, resulting in excessive oil rise. A further disadvantage resides in the fact that cooling of the lower portion of the electric motor is not necessarily sufficient.